We're used to calculating carbon efficiency, or how much CO
2 is produced along with a unit of energy. But there's a lot more to the environmental equation than how much carbon gets produced. We've also got to consider things like heavy metals, particulate production, and habitat impacted.
Increasingly, another environmental concern is starting to pop up when considering power generation. Already, many parts of the world are experiencing serious fresh water shortages, and that isn't helped because many methods of generating power also consume massive amounts of water.
A recent study was published yesterday by researchers at the Virginia Polytechnic Institute quantifying a bunch of different factors in water use in the energy industry. Some of the figures are staggering. Using America's current power mix, it takes up to 6,000 gallons of fresh water to keep a 60 watt light bulb lit for 12 hours a day for a year. Most of this energy is consumed as a cooling fluid at power plants.
The most water-efficient power generating sources were wind, geothermal and hydroelectric plants. While nuclear power plants, with their massive cooling towers, use the most water per watt produced. They were quick to point out that while bio-fuels were more carbon-efficient than fossil fuel alternatives like gasoline, they are far less water-efficient, already adding significantly to the world's water shortages.